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Pastes of ceramic particles are used in many industrial applications such as in printed electronic products and solid oxide fuel cells. Ethyl cellulose (EC), a polymer component in the paste, is very useful to control the rheological properties of the pastes for screen printing. In this study, to prepare ceramic La 0.6 Sr 0.4 Ti 0.3 Fe 0.7 O 3−δ (LSTF) pastes, EC was mixed with an organic solvent, ethylene glycol monobutyl ether acetate, and LSTF powder. The effects of EC and LSTF particle contents were investigated on the rheological properties of the pastes, using shear, stress, frequency-dependence, and a 3-step recovery tests. The recovery ratio of the pastes in the 3-step tests was found to depend strongly on their EC and LSTF particle contents, decreasing at higher contents due to the formation of a strong network. We also investigated the microstructure and surfaces of thick films fabricated through screen-printing, and confirmed that pastes with a low recovery ratio and high viscosity afford smooth surface profiles. [ABSTRACT FROM AUTHOR]

High temperature stability of perovskite oxide is important for the application of cathode materials in solid oxide fuel cells (SOFCs) and oxygen-permeable conductors. The thermal expansion behavior of perovskite oxides with the formula, La 0.6 Sr 0.4 Ti x Fe 1− x O 3− δ (LSTF, x =0, 0.1, 0.2, and 0.3) were measured in both air and a H 2 atmospheres and were investigated using thermogravimetry (TG), powder X-ray diffractometry, and X-ray absorption spectroscopy. The additional expansion caused by reduction of transition metals in the H 2 atmosphere was observed over 200 °C and the rate of increase in expansion became slow above 400 °C for all compositions. While LSF ( x =0) showed large thermal expansion ratio, Δ L / L , of 1.089% in the H 2 atmosphere at 400 °C, that of LSTF ( x =0.3) was reduced to 0.548%. This difference of Δ L / L corresponded to the decrease of the oxygen anion non-stoichiometry, δ , estimated by TG analysis, from 0.20 to 0.07 with x =0, and 0.3, respectively. The Fe cation valence of LSTF was also studied by in-situ X-ray absorption near edge structure in both air and a H 2 atmosphere over the range of 25 to 800 °C, and compared to the Fe cation valances estimated from the values of δ . The valence states Fe and Ti in LSTF and the differences in the reducing kinetics for Ti substitution are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Ethyl cellulose (EC) was mixed with terpineol and conductive ceramic La0.6Sr0.4Ti0.3Fe0.7O3−δ to prepare pastes with different EC content. Viscosity of the vehicles was found to increase with EC content, and the intrinsic viscosity, hydrodynamic radius, and effective sphere of EC in terpineol were estimated to be 0.07L/g, 78.8nm, and 0.06L/g, respectively. For a ceramic paste of 70wt% powder and vehicle, shear thinning properties were observed for pastes of 0 and 1wt% EC. For EC contents above 3wt%, the pastes become Newtonian-like behavior and EC was considered to act effectively as a dispersant. Screen printing of the pastes was carried out. The relative densities of the sintered films were as low as 51.7% for the 0wt% EC paste, but increased to 67.6% for the 3wt% EC paste. The high density observed for the 3wt% EC paste was due to particles being well dispersed, which was also expected from the rheological results. [Copyright &y& Elsevier]

Abstract: The flow behavior of ceramic pastes with various alumina powder contents and different particle sizes, L-particles (D ave. =6.7μm) and S-particles (D ave. =0.13μm), in an organic binder of ethylene–vinyl acetate copolymer and stearic acid was investigated by dynamic viscoelasticity measurements. The rheological properties of ceramic pastes with high powder content over 19vol% could not be investigated by the rotational method due to the high viscosity, and were analyzed by the oscillation method. Relative dynamic complex viscosities increased with the powder content, and were consistent with the Dougherty–Krieger model for evaluation of the apparent hydrodynamic shape factor (K H) and the maximum powder content (). The and K H of the L-paste were 0.62 and 1.6, and those of the S-paste were 0.59 and 8.2, respectively. It is considered that the L-particles were comparatively well dispersed and S-particles were aggregated in the paste. These analyses agreed with the aggregates of S-particles determined by SEM observations. [Copyright &y& Elsevier]